Scientists Are Worried About Air Quality and Dementia Risk

By Jonathan Springston, Editor, Relias Media

Investigators recently noticed a possible association between particulate matter and a higher risk for dementia.

Fine particulate matter is an airborne pollutant produced primarily through car and truck traffic, but also via wildfires and other open burning, along with construction and agricultural operations. As of 2012, the EPA considers an average annual exposure up to 12 micrograms per cubic meter as safe.

Seeking to learn more about the possible specific risks to neurological health, a group of Canadian investigators conducted a meta-analysis. They found studies about not only fine particulate matter, but also nitrogen oxides, nitrogen dioxide, and ozone. Two independent investigators extracted data from 17 studies. The total population was more than 91 million people, all of whom were older than age 40 years. The main outcome was the pooled hazard ratio for dementia per increment of pollutant, calculated using a random-effects model.

The authors reported 5.5 million people (6%) developed dementia. The risk of dementia increased by 3% for every one microgram per cubic meter increase of fine particulate matter exposure. There was a non-significant association between dementia risk and the other three pollutants.

“Our hope is these findings empower people to take an active role in reducing their exposure to pollution,” said study author Ehsan Abolhasani, MD, MSc, of Western University in London, Canada. “By understanding the risk of dementia through exposure to air pollution, people can take steps to reduce their exposure, such as using sustainable energy, choosing to live in areas with lower levels of pollution, and advocating for reduced traffic pollution in residential areas.”

The observational nature of this most recent effort by Abolhasani and colleagues does not prove a definitive connection, only a possible association. Additionally, although there were millions of people in the cohort, the authors said 17 studies is just a small sample. They also noted the “high heterogeneity of effects across studies.”

Even though more studies are necessary, this is a serious problem. Two days before the release of the Canadian study, the American College of Physicians (ACP) published a six-point policy recommendation to address the climate crisis and alleviate exposure to hazardous substances and air and water pollution.

“Environmental harms are much broader than just climate change. Nearly a quarter of global deaths are caused by modifiable environmental factors. We need to be doing more to prevent those deaths,” said ACP President Ryan D. Mire, MD, FACP. “We need aggressive action to deal with climate change, stronger policies on air pollution, clean water for everyone, and to limit exposures to noxious chemicals and other toxins. The health of all of us depends on it.”

For more on this and related subjects, be sure to read the latest issues of Neurology Alert.